Have a young adult male who has stopped eating. For a few days, he would eat nothing at all but he will now only eat ''junk food'' (by this I mean nuts)

Has a usual diet of fruit, veg and Henrys blocks. Totally went off the blocks after just a few weeks of having them, and now gone off everything but treat type foods which he stores away and only eats in private. (usual behaviour has him happy to eat on us)

He is not lethargic or anything, fur looks good, weight is still ok (he was maybe a little podgy, to begin with, I admit)

**EDIT last couple of days he is more skittish than normal, I'm hoping it's due to visitors we had 2 days ago and he was startled**